1. Field of the Invention
This invention relates to an optical information medium printable on a surface thereof opposite to the incidence of laser beam by use of a printing ink, and a method for fabricating the same.
2. Description of the Prior Art
In the fields such as of audio and information processings, an optical information medium called as a compact disk (hereinafter referred to simply as CD) has now been in wide use. The CD has a structure comprising a substrate in the form of a doughnut-shaped disk made, for example, of polycarbonates, and a reflective layer of gold or aluminium vacuum deposited on the substrate. A protective layer such as of a UV-cured resin is formed on the reflective layer. Information data are encoded by forming projected and recessed pits on or in the surface of the substrate according to a spiral arrangement. Simultaneously with the formation of the substrate, these pits have been formed using molds such as stampers. The reflective layer is then formed on the pits- bearing substrate. When fabricated, the CD has already had the data encoded therein and can be thus used as a read-only optical information medium.
Usual practice is that the CD has an index indicating a recorded content and a variety of designs printed on the surface of the protective layer with use of a UV-curable or oily ink. These prints have been usually made by a printing means or procedure using transfer from a printing plate, such as screening printing, tampon printing or offset printing. These printing procedures are ones which are particularly suitable for so-called mass printing wherein the same pattern is printed in great number at one time.
On the other hand, musical performance by amateur players has recently become enthusiastic. As a wide variety of amateur players are being taken part in such performance, it has become full of activities that amateur players individually make a relatively small number of CDs of their own work. These CD articles are created for the purposes, for example, of promotion, audition, test and setting up on their own expenses. Especially, because write-once optical information mediums which are so-called CD-WO and in which information can be written once by use of a laser beam and can be reproduced with use of a CD player have now been developed, such a self-made CD can be made more readily. Alternatively, in the field of computers, so-called CD-ROM has become popular. As the write-once optical information medium has spread, users have now started to set up CD-ROM using CD-WO.
The protective layer of the optical information medium such as the thus self-made CD has no statement thereon, or has general letters or patterns alone printed thereon by means of a UV-curable ink or oily ink. It is thus necessary to indicate the index of a record content and, if necessary, other designs, on the surface of the protective layer or the printed surface of a label prior to or after recording of private information in the optical information medium.
However, the aforementioned printing procedure or means is used to print during the course of the fabrication process of the medium after formation of the protective layer. Since both protective layer surface and print surface are hydrophobic in nature, an excessive equipment becomes necessary in order to print the protective layer on the surface thereof after recording of the private information. This eventually makes it difficult to arbitrarily print personal and optionally desired information. Accordingly, it is usual to draw on the surface of the protective layer by use of an oily felt tipped pen or to paste a label on the surface. However, this requires to hand-write one by one, thus being troublesome. In addition, the drawn patterns or their quality will not be made uniform with a poor show, thus presenting such problems as that the optical information medium obtained is of less elegant format as a whole and might be damaged due to hand-writing. Especially, where a label is pasted, the surface is raised by the thickness of the pasted label, leading to the problem that the optical information medium will undesirably undergo eccentric revolutions or surface fluctuation when reproduced and followed up.